1960s: All young men are required to register for the selective service and face being drafted into the armed forces to serve in Vietnam. While some young men of wealth and privilege escape the draft by enrolling in college, other objectors who are less fortunate flee to Canada to avoid service, or openly defy the draft and face criminal charges. Former heavy weight champion Muhammad Ali, then Cassius Clay, is among those conscientious objectors who choose jail over military service.

1990s: Though all young men are still required to register with the selective service when they turn eighteen, the United States armed forces have been strictly voluntary since Nixon ended the draft in 1972.

1960s: With the Cold War at its peak, America's foreign policy is aimed at stopping the spread of communism in every far-flung corner of the world. Military and political leaders use...